Focus detection system and lighting device therefor

Abstract

A lighting device such as an electronic flash device attachable to a camera body includes first and second light projecting optical systems which project first and second light fluxes for illuminating an object to aid focus detection by a focus detection device. The second light flux spreads at a larger solid angle than the first light flux and illuminates a first distance zone which extends to a closer distance side while covering the whole of a second distance zone illuminated by the first light flux. An optical wedge disposed in the second light projecting optical system deflects a part of the second light flux towards the closer distance side of the first distance zone. Another lighting device includes a single light projecting optical system but it also includes an optical wedge for deflecting a part of a light flux projected by the light projecting optical system to widen a distance zone illuminated by the light flux towards a closer distance. The optical wedge also serves to produce a difference in intensity distribution of the light flux such that the light flux has higher intensity at a part thereof for illuminating a farther distance side of the distance zone than at a part thereof for illuminating a closer distance side of the distance zone. A light source of the light projecting optical system(s) is provided with a conical light reflecter surrounding a light emitting diode to reflect light emitted from side surfaces of the light emitting diode forward.

What is claimed is: 
     
       1. A focus detection system for detecting focus condition of an objective lens of a camera with respect to an object within a focus detection area which spreads at a solid angle centering at the optical axis of said objective lens, comprising: a light projecting optical system for projecting a flux of light which crosses said focus detection area at a predetermined angle;   a light source for emitting light, said light source including:   a light emitting diode adapted to emit said light from its front surface and its side surfaces;   a transparent molded member disposed in front of said front surface of said light emitting diode and having a spherical surface;   a concave light reflective member surrounding said side surfaces of said light emitting diode to reflect said light emitted from said side surfaces of said light emitting diode towards said transparent molded member;   a projective pattern including a plurality of alternatively arranged transparent portions and opaque portions; and   a projecting lens for projecting said light forward as said flux of light, wherein said light source fulfills the following conditions:   0.6<l/R<1.1       l=h-R        wherein: h represents a distance between the top of the spherical surface of the transparent molded member and the front face of the light emitting diode; and R represents a radius of curvature of the transparent molded member.   
     
     
       2. A focus detection system for detecting focus condition of an objective lens of a camera with respecft to an object within a focus detection area which spreads at a solid angle centering at the optical axis of said objective lens, comprising: a light projecting optical system for projecting a flux of light which crosses said focus detection area at a predetermined angle;   a light source for emitting light, said light source including:   a light emitting diode adapted to emit said light from its front surface and its side surfaces;   a transparent molded member disposed in front of said front surface of said light emitting diode and having a spherical surface;   a concave light reflective member surrounding said side surfaces of said light emitting diode to reflect said light emitted from said side surfaces of said light emitting diode towards said transparent molded member;   a projective pattern including a plurality of alternatively arranged transparent portions and opaque portions; and   a projecting lens for projecting said light forward as said flus of light, wherein said light source fulfills the following conditions:   0.8<l/R<1.3       l=h-R        wherein: h represents a distance between the top of the spherical surface of the transparent molded member and the front face of the light emitting diode; and R represents a radius of curvature of the transparent molded member.   
     
     
       3. An accessory for use with a camera having a focus detection system for detecting focus condition of an objective lens of said camera with respect to an object within a focus detection area which spreads at a solid angle centering at the optical axis of said objective lens, said accessory comprising: a light projecting optical system for projecting a flux of light which crosses said focus detection area at a predetermined angle;   a light source for emitting light, said light source including:   a light emitting diode adapted to emit said light from its front surface and its side surfaces;   a transparent molded member disposed in front of said front surface of said light emitting diode and having a spherical surface;   a concave light reflective member surrounding said side surfaces of said light emitting diode to reflect sad from said side surfaces of said light emitting diode towards said transparent molded member;   a projective pattern including a plurality of alternatively arranged transparent portions and opaque oprtions; and   a projecting lens for projecting said light forward as said flux of light, wherein said light source fulfills the following conditions:   0.6<l/R<p1.1       l=h-R        wherein: h represents a distance between the top of the spherical surface of the transparent molded member and the front face of the light emitting diode; and R represents a radius of curvature of the transparent molded member.   
     
     
       4. An accessory for use with a camera having a focus detection system for detecting focus condition of an objective lens of said camera with respect to an object within a focus detection area which spreads at a solid angle centering at the optical axis of said objective lens, said accessory comprising: a light projecting optical system for projecting a flux of light which crosses said focus detection area at a predetermined angle;   a light source for emitting light, said light source including:   a light emitting diode adapted to emit said light from its front surface and its side surfaces;   a transparent molded member disposed in front of said front surface of said light emitting diode and having a spherical surface;   a concave light reflective member surrounding said side surfaces of said light emitting diode to reflect said light emitted from said side surfaces of said light emitting diode towards said transparent molded member;   a projective pattern including a plurality of alternatively arranged transparent portions and opaque portions; and   a projecting lens for projecting said light forward as said flux of light, wherein said light source fulfills the following conditions:   
     
     
       0. 8<l/R<1.3   l=h-R      wherein: h represents a distance between the top of the spherical surface of the transparent molded member and the front face of the light emitting diode; and R represents a radius of curvature of the transparent molded member.